1. Field of the Invention
The present invention relates to a lens device and more particularly, to a lens device including a rear focus lens.
2. Description of the Related Art
JP-A-2007-219023 discloses a rear-focus-type lens device used in a portable ENG (Electronic News Gathering) camera for television news.
A rear-focus-type lens device has been proposed in which a switch is provided on the front side of the lens barrel body, but a structure has not been disclosed in which a plurality of switches for operating the lens device is provided in a rear fixed cylinder having, for example, a focus lens accommodated therein. In the lens device according to the related art, the lens barrel body is larger than the lens and there is an empty space for arranging a plurality of switches or a flexible printed circuit board.
However, in the lens device according to the related art, it is difficult to ensure an empty space for arranging a plurality of switches in front of the lens barrel body due to a reduction in the size of the rear-focus-type lens device.
For this reason, in the rear-focus-type lens device, a plurality of switches is provided in the rear fixed cylinder (attachment frame) having, for example, the focus lens accommodated therein.
FIG. 13 is a perspective view illustrating an attachment frame at the beginning of development. As shown in FIG. 13, an opening 3 to which a switch cover (not shown) having a plurality of switches provided thereon is attached is formed in the side surface of the attachment frame 2 and a rib 4 is provided in the attachment frame 2 so as to avoid parts provided on the rear surface of the switch cover.
However, although the rib 4 is formed in the attachment frame 2, about one-third of the side surface of the attachment frame is cut out. Therefore, the strength of the attachment frame and the accuracy of the parts are reduced.